BACKGROUND: Oral anticoagulation is suggested in patients with atrial fibrillation and a CHA ₂ DS ₂ -VASc score ≥1 (congestive heart failure, hypertension, age ≥75 years, diabetes, stroke, vascular disease, age 65–74 years, and sex score). To assess granular differences within CHA ₂ DS ₂ -VASc 1, the incidence of arterial thromboembolism according to CHA ₂ DS ₂ -VASc 1 subgroups was examined. METHODS: The Danish National Patient Registry and the Danish Prescription Registry were linked on a nationwide level to identify patients with atrial fibrillation from 2000 to 2021 without oral anticoagulation and categorized according to CHA ₂ DS ₂ -VASc score: CHA ₂ DS ₂ -VASc 0 (male and female subjects); CHA ₂ DS ₂ -VASc 1 (hypertension, heart failure, diabetes, vascular disease, and age 65–74 years); or CHA ₂ DS ₂ -VASc 2 (age ≥75 years without other risk factors). Female sex was not considered a risk factor in any risk group. The outcome was arterial thromboembolism (ischemic stroke, embolism of extremity, or transient cerebral ischemia). Study groups were compared using Cox regression analysis. RESULTS: We included 26 701 patients with a CHA ₂ DS ₂ -VASc 0 score; 22 915 with CHA ₂ DS ₂ -VASc 1 (1483 patients with heart failure, 9066 with hypertension, 843 with diabetes, 770 with vascular disease, and 10 753 who were 65 to 74 years of age); and 14 525 patients with CHA ₂ DS ₂ -VASc 2 (≥75 years of age without other risk factors). With a median of 1 year of observation time, the cumulative incidence of arterial thromboembolism was 0.6% (n=154 [95% CI, 0.6%–0.8%]), 1.4% (n=16 [95% CI, 0.8%–2.2%]), 1.9% (n=141 [95% CI, 1.6%–2.2%]), 1.7% (n=12 [95% CI, 0.9%–2.9%]), 2.0% (n=13 [95% CI, 1.1%–3.4%]), 2.3% (n=187 [95% CI, 2.0%–2.7%]), and 4.4% (n=533 [95% CI, 4.1%–4.8%]) for CHA ₂ DS ₂ -VASc 0, heart failure, hypertension, diabetes, vascular disease, age 65 to 74 years (CHA ₂ DS ₂ -VASc 1), and age ≥75 years (CHA ₂ DS ₂ -VASc 2), respectively. No statistically significant difference was identified among subgroups of CHA ₂ DS ₂ -VASc 1 ( P =0.15 for difference). CONCLUSIONS: For patients with atrial fibrillation, all subgroups of CHA ₂ DS ₂ -VASc 1 were associated with lower incidence of arterial thromboembolism compared with age ≥75 years without other risk factors (ie, CHA ₂ DS ₂ -VASc 2) and a higher incidence compared with CHA ₂ DS ₂ -VASc 0. No statistically significant difference was identified between the subgroups of CHA ₂ DS ₂ -VASc 1. These findings support current recommendations that patients within this intermediate risk group could be identified with a similar risk of arterial thromboembolism.